The semiconductor industry is increasing its use of integrated circuits. In particular, there is a demand for silicon-on-insulator structures comprising a "mushroom" shape, i.e., a relatively narrow "stem" of silicon grown through an oxide layer and having a silicon "head," of larger lateral dimension than the "stem," grown on top of the stem in such a manner that a portion of the "head" is positioned on top of the oxide layer. Such a structure is shown in European patent application No. 81104511.1, filed 11.06.81.
When the "mushroom" shape is formed by growing silicon, first vertically and then laterally over a step in the oxide layer, the silicon grown over the step has a tendency to become polycrystalline. As a result, devices such as a Silicon-On-Insulator-Like (SOIL) insulated gate field effect transistor (IGFET) fabricated in this manner may have degraded performance.
As a result, it is desirable to have a method for reliably growing a monocrystalline (single crystal) semiconductor, and in particular, single crystal silicon in a "mushroom" shape.